ADD -- Add (with overflow)
Description:
Adds two registers and stores the result in a register
Operation:
$d = $s + $t; advance_pc (4);
Syntax:
add $d, $s, $t
Encoding:
0000 00ss ssst tttt dddd d000 0010 0000
ADDI -- Add immediate (with overflow)
Description:
Adds a register and a sign-extended immediate value and stores the result in a register
Operation:
$t = $s + imm; advance_pc (4);
Syntax:
addi $t, $s, imm
Encoding:
0010 00ss ssst tttt iiii iiii iiii iiii
ADDIU -- Add immediate unsigned (no overflow)
Description:
Adds a register and a sign-extended immediate value and stores the result in a register
Operation:
$t = $s + imm; advance_pc (4);
Syntax:
addiu $t, $s, imm
Encoding:
0010 01ss ssst tttt iiii iiii iiii iiii
ADDU -- Add unsigned (no overflow)
Description:
Adds two registers and stores the result in a register
Operation:
$d = $s + $t; advance_pc (4);
Syntax:
addu $d, $s, $t
Encoding:
0000 00ss ssst tttt dddd d000 0010 0001
AND -- Bitwise and
Description:
Bitwise ands two registers and stores the result in a register
Operation:
$d = $s & $t; advance_pc (4);
Syntax:
and $d, $s, $t
Encoding:
0000 00ss ssst tttt dddd d000 0010 0100
ANDI -- Bitwise and immediate
Description:
Bitwise ands a register and an immediate value and stores the result in a register
Operation:
$t = $s & imm; advance_pc (4);
Syntax:
andi $t, $s, imm
Encoding:
0011 00ss ssst tttt iiii iiii iiii iiii
BEQ -- Branch on equal
Description:
Branches if the two registers are equal
Operation:
if $s == $t advance_pc (offset << 2)); else advance_pc (4);
Syntax:
beq $s, $t, offset
Encoding:
0001 00ss ssst tttt iiii iiii iiii iiii
BGEZ -- Branch on greater than or equal to zero
Description:
Branches if the register is greater than or equal to zero
Operation:
if $s >= 0 advance_pc (offset << 2)); else advance_pc (4);
Syntax:
bgez $s, offset
Encoding:
0000 01ss sss0 0001 iiii iiii iiii iiii
BGEZAL -- Branch on greater than or equal to zero and link
Description:
Branches if the register is greater than or equal to zero and saves the return address in $31
Operation:
if $s >= 0 $31 = PC + 8 (or nPC + 4); advance_pc (offset << 2)); else advance_pc (4);
Syntax:
bgezal $s, offset
Encoding:
0000 01ss sss1 0001 iiii iiii iiii iiii
BGTZ -- Branch on greater than zero
Description:
Branches if the register is greater than zero
Operation:
if $s > 0 advance_pc (offset << 2)); else advance_pc (4);
Syntax:
bgtz $s, offset
Encoding:
0001 11ss sss0 0000 iiii iiii iiii iiii
BLEZ -- Branch on less than or equal to zero
Description:
Branches if the register is less than or equal to zero
Operation:
if $s <= 0 advance_pc (offset << 2)); else advance_pc (4);
Syntax:
blez $s, offset
Encoding:
0001 10ss sss0 0000 iiii iiii iiii iiii
BLTZ -- Branch on less than zero
Description:
Branches if the register is less than zero
Operation:
if $s < 0 advance_pc (offset << 2)); else advance_pc (4);
Syntax:
bltz $s, offset
Encoding:
0000 01ss sss0 0000 iiii iiii iiii iiii
BLTZAL -- Branch on less than zero and link
Description:
Branches if the register is less than zero and saves the return address in $31
Operation:
if $s < 0 $31 = PC + 8 (or nPC + 4); advance_pc (offset << 2)); else advance_pc (4);
Syntax:
bltzal $s, offset
Encoding:
0000 01ss sss1 0000 iiii iiii iiii iiii
BNE -- Branch on not equal
Description:
Branches if the two registers are not equal
Operation:
if $s != $t advance_pc (offset << 2)); else advance_pc (4);
Syntax:
bne $s, $t, offset
Encoding:
0001 01ss ssst tttt iiii iiii iiii iiii
DIV -- Divide
Description:
Divides $s by $t and stores the quotient in $LO and the remainder in $HI
Operation:
$LO = $s / $t; $HI = $s % $t; advance_pc (4);
Syntax:
div $s, $t
Encoding:
0000 00ss ssst tttt 0000 0000 0001 1010
DIVU -- Divide unsigned
Description:
Divides $s by $t and stores the quotient in $LO and the remainder in $HI
Operation:
$LO = $s / $t; $HI = $s % $t; advance_pc (4);
Syntax:
divu $s, $t
Encoding:
0000 00ss ssst tttt 0000 0000 0001 1011
J -- Jump
Description:
Jumps to the calculated address
Operation:
PC = nPC; nPC = (PC & 0xf0000000) | (target << 2);
Syntax:
j target
Encoding:
0000 10ii iiii iiii iiii iiii iiii iiii
JAL -- Jump and link
Description:
Jumps to the calculated address and stores the return address in $31
Operation:
$31 = PC + 8 (or nPC + 4); PC = nPC; nPC = (PC & 0xf0000000) | (target << 2);
Syntax:
jal target
Encoding:
0000 11ii iiii iiii iiii iiii iiii iiii
JR -- Jump register
Description:
Jump to the address contained in register $s
Operation:
PC = nPC; nPC = $s;
Syntax:
jr $s
Encoding:
0000 00ss sss0 0000 0000 0000 0000 1000
LB -- Load byte
Description:
A byte is loaded into a register from the specified address.
Operation:
$t = MEM[$s + offset]; advance_pc (4);
Syntax:
lb $t, offset($s)
Encoding:
1000 00ss ssst tttt iiii iiii iiii iiii
LUI -- Load upper immediate
Description:
The immediate value is shifted left 16 bits and stored in the register. The lower 16 bits are zeroes.
Operation:
$t = (imm << 16); advance_pc (4);
Syntax:
lui $t, imm
Encoding:
0011 11-- ---t tttt iiii iiii iiii iiii
LW -- Load word
Description:
A word is loaded into a register from the specified address.
Operation:
$t = MEM[$s + offset]; advance_pc (4);
Syntax:
lw $t, offset($s)
Encoding:
1000 11ss ssst tttt iiii iiii iiii iiii
MFHI -- Move from HI
Description:
The contents of register HI are moved to the specified register.
Operation:
$d = $HI; advance_pc (4);
Syntax:
mfhi $d
Encoding:
0000 0000 0000 0000 dddd d000 0001 0000
MFLO -- Move from LO
Description:
The contents of register LO are moved to the specified register.
Operation:
$d = $LO; advance_pc (4);
Syntax:
mflo $d
Encoding:
0000 0000 0000 0000 dddd d000 0001 0010
MULT -- Multiply
Description:
Multiplies $s by $t and stores the result in $LO.
Operation:
$LO = $s * $t; advance_pc (4);
Syntax:
mult $s, $t
Encoding:
0000 00ss ssst tttt 0000 0000 0001 1000
MULTU -- Multiply unsigned
Description:
Multiplies $s by $t and stores the result in $LO.
Operation:
$LO = $s * $t; advance_pc (4);
Syntax:
multu $s, $t
Encoding:
0000 00ss ssst tttt 0000 0000 0001 1001
NOOP -- no operation
Description:
Performs no operation.
Operation:
advance_pc (4);
Syntax:
noop
Encoding:
0000 0000 0000 0000 0000 0000 0000 0000
Note: The encoding for a NOOP represents the instruction SLL $0, $0, 0 which has no side effects. In fact, nearly every instruction that has $0 as its destination register will have no side effect and can thus be considered a NOOP instruction.
OR -- Bitwise or
Description:
Bitwise logical ors two registers and stores the result in a register
Operation:
$d = $s | $t; advance_pc (4);
Syntax:
or $d, $s, $t
Encoding:
0000 00ss ssst tttt dddd d000 0010 0101
ORI -- Bitwise or immediate
Description:
Bitwise ors a register and an immediate value and stores the result in a register
Operation:
$t = $s | imm; advance_pc (4);
Syntax:
ori $t, $s, imm
Encoding:
0011 01ss ssst tttt iiii iiii iiii iiii
SB -- Store byte
Description:
The least significant byte of $t is stored at the specified address.
Operation:
MEM[$s + offset] = (0xff & $t); advance_pc (4);
Syntax:
sb $t, offset($s)
Encoding:
1010 00ss ssst tttt iiii iiii iiii iiii
SLL -- Shift left logical
Description:
Shifts a register value left by the shift amount listed in the instruction and places the result in a third register. Zeroes are shifted in.
Operation:
$d = $t << h; advance_pc (4);
Syntax:
sll $d, $t, h
Encoding:
0000 00ss ssst tttt dddd dhhh hh00 0000
SLLV -- Shift left logical variable
Description:
Shifts a register value left by the value in a second register and places the result in a third register. Zeroes are shifted in.
Operation:
$d = $t << $s; advance_pc (4);
Syntax:
sllv $d, $t, $s
Encoding:
0000 00ss ssst tttt dddd d--- --00 0100
SLT -- Set on less than (signed)
Description:
If $s is less than $t, $d is set to one. It gets zero otherwise.
Operation:
if $s < $t $d = 1; advance_pc (4); else $d = 0; advance_pc (4);
Syntax:
slt $d, $s, $t
Encoding:
0000 00ss ssst tttt dddd d000 0010 1010
SLTI -- Set on less than immediate (signed)
Description:
If $s is less than immediate, $t is set to one. It gets zero otherwise.
Operation:
if $s < imm $t = 1; advance_pc (4); else $t = 0; advance_pc (4);
Syntax:
slti $t, $s, imm
Encoding:
0010 10ss ssst tttt iiii iiii iiii iiii
SLTIU -- Set on less than immediate unsigned
Description:
If $s is less than the unsigned immediate, $t is set to one. It gets zero otherwise.
Operation:
if $s < imm $t = 1; advance_pc (4); else $t = 0; advance_pc (4);
Syntax:
sltiu $t, $s, imm
Encoding:
0010 11ss ssst tttt iiii iiii iiii iiii
SLTU -- Set on less than unsigned
Description:
If $s is less than $t, $d is set to one. It gets zero otherwise.
Operation:
if $s < $t $d = 1; advance_pc (4); else $d = 0; advance_pc (4);
Syntax:
sltu $d, $s, $t
Encoding:
0000 00ss ssst tttt dddd d000 0010 1011
SRA -- Shift right arithmetic
Description:
Shifts a register value right by the shift amount (shamt) and places the value in the destination register. The sign bit is shifted in.
Operation:
$d = $t >> h; advance_pc (4);
Syntax:
sra $d, $t, h
Encoding:
0000 00-- ---t tttt dddd dhhh hh00 0011
SRL -- Shift right logical
Description:
Shifts a register value right by the shift amount (shamt) and places the value in the destination register. Zeroes are shifted in.
Operation:
$d = $t >> h; advance_pc (4);
Syntax:
srl $d, $t, h
Encoding:
0000 00-- ---t tttt dddd dhhh hh00 0010
SRLV -- Shift right logical variable
Description:
Shifts a register value right by the amount specified in $s and places the value in the destination register. Zeroes are shifted in.
Operation:
$d = $t >> $s; advance_pc (4);
Syntax:
srlv $d, $t, $s
Encoding:
0000 00ss ssst tttt dddd d000 0000 0110
SUB -- Subtract
Description:
Subtracts two registers and stores the result in a register
Operation:
$d = $s - $t; advance_pc (4);
Syntax:
sub $d, $s, $t
Encoding:
0000 00ss ssst tttt dddd d000 0010 0010
SUBU -- Subtract unsigned
Description:
Subtracts two registers and stores the result in a register
Operation:
$d = $s - $t; advance_pc (4);
Syntax:
subu $d, $s, $t
Encoding:
0000 00ss ssst tttt dddd d000 0010 0011
SW -- Store word
Description:
The contents of $t is stored at the specified address.
Operation:
MEM[$s + offset] = $t; advance_pc (4);
Syntax:
sw $t, offset($s)
Encoding:
1010 11ss ssst tttt iiii iiii iiii iiii
SYSCALL -- System call
Description:
Generates a software interrupt.
Operation:
advance_pc (4);
Syntax:
syscall
Encoding:
0000 00-- ---- ---- ---- ---- --00 1100
The syscall instruction is described in more detail on the System Calls page.
XOR -- Bitwise exclusive or
Description:
Exclusive ors two registers and stores the result in a register
Operation:
$d = $s ^ $t; advance_pc (4);
Syntax:
xor $d, $s, $t
Encoding:
0000 00ss ssst tttt dddd d--- --10 0110
XORI -- Bitwise exclusive or immediate
Description:
Bitwise exclusive ors a register and an immediate value and stores the result in a register
Operation:
$t = $s ^ imm; advance_pc (4);
Syntax:
xori $t, $s, imm
Encoding:
0011 10ss ssst tttt iiii iiii iiii iiii
